Serum glycoproteins isolated from certain antarctic fishes have an extraordinary capability for depressing the freezing point of water. When solutions of the glycoproteins are frozen they are not concentrated in the liquid phase as are most salts. Moreover, in the presence of the glycoproteins, salts are also not concentrated. These properties suggest that the glycoproteins will be extremely useful for studying cryoprotection. We propose to investigate their usefulness as cryoprotective agents for human red blood cells, spermatozoa, tumor cells and heart tissue. To understand how the glycoproteins might confer protection during freezing we will investigate how they interact with water and how they prevent concentration of salts. To determine whether the glycoproteins' freezing-modifying effects are due to their ability to bind water, NMR measurements of bound water, measurements of exchange rates of tritiated water through dialysis membrane, and measurements of freezing point depression of solvents other than water will be made in the presence of native and chemically modified inactive glycoproteins.